Preheat the oven to 370°F. Butter and flour a 10” loose base cake tin. Mash the bananas using a fork. Beat the butter and sugar. Add the eggs 1 at a time, beating on high speed. Combine the dry ingredients and the toffees. Fold the flour mixture into the batter, alternating with the banana mash. Pour into the tin and bake on the lowest rack of the oven for about 45 minutes. For the topping, measure all ingredients into a pan and stir. Cook for a few minutes. Spoon the mixture onto the prebaked cake. Keep baking for about 10 minutes or until the cake is baked through. Check with a stick. If the top of the cake is brown but the cake is still underbaked, cover with tin foil. Before inverting it, let the cake rest for about 15 minutes in the tin. Leave the tin over the cake in order to keep the cake moist. Serve as such or with vanilla ice cream.